. "An object of the present invention is to provide an antimony pentoxide sol which can be well dispersed in a cationic resin emulsion, a cationic water-soluble polymer solution, inorganic and organic acid, aqueous solutions containing the metal salts or organic amine salts of these acids, and organic solvents such as alcohols, in which antimony pentoxide sols of the prior art could be dispersed with" . . . .